Data backup apparatus of a semiconductor memory

1. A data backup apparatus, comprising: a semiconductor memory having a plurality of independently addressable areas; a writing unit for writing a first data value to at least four and even number of areas of the independently addressable areas, the writing unit writing the first data value in the four areas one independently addressable area at a time; a reading unit for reading second data values from the four areas; coincidence determining means for determining whether more than half of the second data values read from the four areas have a same value; and assigning means for determining a coincidence value when said coincidence determining means has determined that more than half of the second data values are the same value and assigning the coincidence value to an output of the reading unit.

2. The apparatus according to claim 1, wherein not more than two addresses of the at least four areas are successive.

3. The apparatus according to claim 1, wherein said reading unit serially reads the second data values from the at least four areas in an ascending order of addresses of the four areas and the writing unit sequentially writing the first data value to the four areas in an ascending order of addresses of the independently addressable areas.

4. The apparatus according to claim 1, further comprising detecting means for detecting where a particular data item of a set of data items is renewed, wherein the writing unit writes the particular data item to the at least four areas corresponding to the particular data item of the areas of the memory when said detecting means has detected that the particular data item is renewed.

5. The apparatus according to claim 1, further comprising default value assigning means for assigning a default value to the output of the reading unit when said coincidence determining means has determined that more than half of the second data values are not the same.

6. The apparatus according to claim 1, further comprising common checking means for detecting whether a value read from the at least four areas of the memory is the same as a corresponding first data value when it is detected that none of first data values corresponding to a set of data items is renewed.

7. A data backup apparatus comprising: a non-volatile semiconductor memory having a plurality of areas, each area storing a value of variables; a writing unit for writing a value to a plural number of areas of the memory one by one, the plural number being at least four and even; a reading unit for reading the values from the plural number of areas of the memory; coincidence determining means for determining whether more than half of values read from the plural number of areas of the memory are the same as each other; and assigning means for determining a coincidence value when said coincidence determining means has determined that more than half of the read values are the same, so that the coincidence value is assigned to each variable; wherein each of a first half of the read values has an original bit pattern, and each of a second half of the read values from the non-volatile memory has a reverse bit pattern, and wherein said coincidence determining means determines that more than half of the read values are the same as each other when it is detected that the original bit pattern for the first half of the read values and a double reversed bit pattern for the second half of the read values coincide with each other and that the read values include at least one value having the original bit pattern and at least one value having the double reversed bit pattern.

8. A data backup apparatus, comprising: a semiconductor memory; a writing unit that writes first data values to the memory at different addresses of the memory; a reading unit that reads second data values from the memory at the different addresses; coincidence determining device that determines whether more than half of the second data values read from the memory have a same value; and assigning device that assigns the same value to an output of the reading unit when more than half of the second data values are the same value.

9. The apparatus of claim 8, a number of different addresses being at least four.

10. The apparatus of claim 8, a number of different addresses being an even number.

11. The apparatus of claim 8, at most two of the different addresses are consecutive.

12. The apparatus of claim 8, all the first data values have a same value, the writing unit writing the first data values to a first half of the different addresses and writing one's complement of the first data values to a second half of the different addresses, the coincidence determining device one's complementing second data values read from the second half of the different addresses before determining whether more than half of the second data values have the same value.

13. The apparatus of claim 8, the writing and reading units writing and reading the first and the second data values from the different addresses in an ascending order.

14. A method for backing up data, comprising: writing first data into a memory at different addresses; reading second data from the different addresses; generating a coincidence condition when more than half of the second data have a same value; and assigning the same value as an output value of the reading step if the coincidence condition is generated.

15. The method of claim 14, wherein a number of different addresses is at least four.

16. The method of claim 14, wherein a number of different addresses is an even number.

17. The method of claim 14, at most two of the different addresses are consecutive.

18. The method of claim 14, wherein all the first data values have a same value, the method further comprising: writing the first data values to a first half of the different addresses; writing one's complement of the first data values to a second half of the different addresses; one's complementing second data values read from the second half of the different addresses before determining whether more than half of the second data values have the same value.

19. The method of claim 14, further comprising writing and reading the first and the second data values from the different addresses in an ascending order.